Developing a strategy for cysticercosis control in Rwanda, to reduce the burden of epilepsy

The pig tapeworm is the leading cause of preventable epilepsy worldwide. Adult tapeworms live in the human small intestine, eggs are passed in faeces and if eaten by pigs will develop into larval cysts in muscles. Eating cysts in under-cooked pork completes the life-cycle in humans. However, ingested eggs can also develop into cysts in humans, and if cysts develop in the brain, they can cause neurocysticercosis, with epilepsy the most important symptom. The prevalence of epilepsy is high in low and middle income countries, and around a third of epilepsy cases in endemic areas are thought to be due to tapeworm infection, where poor sanitation enables exposure of pigs and people to infective eggs in human faeces. The burden of disease is particularly high in sub-Saharan Africa, and is likely to increase as pig production and pork consumption is increasing rapidly.

A number of methods are have recently become available to control of pig tapeworm infection. This includes effective drugs to treat pigs and people, and a newly developed vaccine that protects pigs from infection. Using these methods it has been shown to be possible to control the disease in Peru in an intensive control programme. There is now a need to study how best to use these methods to sustainably control infection in African countries such as Rwanda. Rwanda is a small but densely populated country, mostly engaged in subsistence agriculture, with a very low per capita GDP. There has been significant investment in agriculture, including pig introduction, and the pig population has increased dramatically to more than 1 million in the last decade as demand for pork increases. Most pig production is small scale, and is an important source of income for smallholders, but these production methods are associated with a high risk of cysticercosis in neighbouring countries. Cysticercosis is also a large economic cost for pig production, as infection reduces the value of the meat by up to 50%.

There is a clear need for new control initiatives, and Rwanda provides an excellent opportunity, with small size and relatively strong institutions and infrastructure. The prevalence of epilepsy in Rwanda is high, with a severe social stigma attached to the disease. However, there is almost no detailed information available on the prevalence of infection in pigs and humans in Rwanda, nor on the economics of pig production in the country.

Our objectives are to collect these essential data on pig production methods and economics, the prevalence of infection in pork entering the food chain and in pigs and humans across the country, and determine the risk factors for infection in humans and pigs. We will then use these results, and inputs from important stakeholders, to develop a national country strategy. This will include developing economic models for investment in disease control in pigs, such as new markets for disease-free pork, and exploring how private sector business and public sector disease control efforts can be effectively combined. Finally, we will establish a partnership between national government, scientists and disease control experts, to plan the implementation of disease control.

The outcomes of the project will be the first assessment of the importance of cysticercosis in Rwanda for human health and agricultural production, and the development of a national plan for disease control. To achieve these outcomes, we will establish a new collaboration between UK and Rwandan investigators to build local capacity in parasitological research.

Neurocysticercosis from pig tapeworm infection is the leading cause of preventable epilepsy, causing around 30% of epilepsy in endemic areas, with a high burden of disease in sub-Saharan Africa. Tools for effective control are now available. Rwanda provides an excellent opportunity for control, but there is almost no information on the prevalence and distribution of infection, nor the economics of pig production, in the country.
Our aims are to:
(1) collect baseline data on the pig value chain in Rwanda, to understand the stakeholders in and governance of pig production. Interviews, questionnaires and market research will be used in formal value chain mapping approach.
(2) assess the prevalence of infection in pork entering the food chain, and the prevalence of human and porcine cysticercosis across the country. We will use a stratified random sampling approach to estimate infection in different pig production systems and geographic areas. Cysticercosis in humans and pigs will be detected by antigen ELISA, with confirmation in selected pigs by carcass dissection and species-specific PCR.
(3) identify risk factors for infection in a high prevalence area. Risk factors for human cysticercosis and taeniosis (diagnosed by faecal egg counts and copro-antigen ELISA) will be assessed by household questionnaire in a total population survey. Potential risk factors will include demography, sanitation, socioeconomic status (using a wealth index), diet (consumption and cooking of pork), previous anthelminthic treatment and knowledge of the parasite. Households will also be georeferenced, and remote-sensed environmental data obtained.
(4) Finally, we will use these data to develop a control strategy for porcine and human infection, and establish a partnership for disease control. This will include developing enterprise models for market-based initiatives, such as premium markets for certified infection-free meat, together with mass chemotherapy approaches.

Cysticercosis due to the pig tapeworm has the highest burden of disease of any food-borne infection. Infection is the leading cause of preventable epilepsy, which results from infection with the larval cyst stages (neurocysticercosis). About 30% of epilepsy in endemic areas is caused by tapeworm infection. Neurocysticercosis is a particular problem in LMICs, where poor sanitation allows exposure of pigs and people to tapeworm eggs in human faeces. Prevalence of infection and burden of disease is particularly high in sub-Saharan Africa, with up to 50% of pigs infected. Epilepsy results in severe impacts on patients' quality of life, and significant social and economic impacts. These impacts are exacerbated in LMICs, where there is often a severe stigma associated with epilepsy, and where treatment costs can be a large proportion of average annual income. Cysticercosis also has significant economic costs for pig production, with a loss of 30-50% of the value of infected carcasses. Rwanda is a small, densely populated country of 13 million, 90% engaged in subsistence agriculture. Rwanda is a Least Developed Country, with very low per capita GDP (207/229 countries). There is significant ongoing investment in agriculture, with pig production highlighted as an important source of income for smallholders, and the pig population has increased 7-fold to >1 million in the last 20 years. However, smallholder pig production is associated with a high risk of cysticercosis. The prevalence of epilepsy in Rwanda is known to be high, and is expected to rise with the increased pig production. The tools needed for the control of cysticercosis are available, and control of cysticercosis would have significant positive impacts on both human health and the economics of pig production, so control planning is a priority. A necessary prerequisite is to generate evidence through the collection of baseline data on human and pig infection levels across the country, and on the pig industry.

The key outcomes of the project will be estimates of the burden of infection in humans and pigs across Rwanda, and development of a control strategy, including market-based mechanisms to control infection in pigs. Crucially, this project will bring together the public health and agricultural communities through a One Health approach; effective control will require interventions at several points in the parasite life cycle. The project outcomes will be of interest to a range of beneficiaries:
(1) The key stakeholder is the Rwandan government, specifically the Ministries of Health and Agriculture. The project will deliver several outputs to assist with the planning and implementation of effective control measures. The value chain mapping for pig production will also have wider applicability to improving pig production.
(2) The outcomes will also benefit other organisations involved in neglected disease control in Rwanda and in the broader region, including policy-makers, NGOs and funders. Cysticercosis is a serious problem in LMICs across much of sub-Saharan Africa, and elsewhere.
(3) the project will build capacity in cysticercosis research, One Health approaches more generally, and zoonotic disease control in Rwanda. This will benefit the medical and animal science research communities.
(4) pig farmers in Rwanda will benefit from increased knowledge of cysticercosis, and how to detect and prevent infection in pigs.
(5) the project results will be of interest to private sector firms with an interest in investing in the pig sector in East Africa. This region is a large growth market, and neighbouring countries are seeing substantial growth of private sector firms involved in pig production and marketing.
(6) the wider public in Rwanda, including the study participants, can benefit from increased knowledge of the health impacts and transmission routes of the pig tapeworm, which may result in direct health benefits through reduced exposure to infection.